Testing machine grip



P 1965 R. c. CAVANAUGH ETAL 3,204,451

TESTING MACHINE GRIP Filed June 5, 1962 United States Patent 3,204,451 TESTING MACHINE GRIP Ronald C. Cavanaugh, Canton, and Donald C. Holmes,

North Weymouth, Mass, assignors to Instron Corporation, Canton, Mass., a corporation of Massachusetts Filed June 5, 1962, Ser. No. 200,202 Claims. (Cl. 73-103) This invention relates to a grip useful in materials testing machines.

It is a primary object of the present invention to provide a grip useful in testing machines which combines simple and rugged construction with positive action and very low frictional resistance to opening and closing of its jaws. Other objects are to provide such a grip in which the faces of the jaws are at all times under control, free from flopping-around conditions, and are at all times parallel to each other and equidistant from the grip centerline on opposed sides thereof; in which the jaws come together with transverse movement only, free from any longitudinal component of motion, which could result in undesirable precompression of a specimen held between the grip and another grip for stressing therebetween; and in which, in preferred embodiments, any longitudinal movement of a specimen being stressed results in additional transverse movement together of the jaws to further more securely grip the specimen.

Broadly speaking, the invention features a longitudinal core provided at an inner end with mounting means and at an outer end with a transverse guide surface rigidly spaced from the mounting means and extending on each side of the core axis; a pair of jaws slidable on the transverse guide surface for transverse movement thereon; a longitudinally selectively movable frame; and a pair of links, each with one end pivotally secured in said frame and with the other pivotally secured in a jaw. In preferred embodiments, upper and lower transverse guide surfaces are provided at the outer end of the core, and each jaw includes a pair of cooperating surfaces simultaneously slidable thereon. In one preferred embodiment the lower or outer of the transverse guide surfaces is rigidly spaced from the mounting means, and the upper or inner thereof is yieldably limitedly spaced away from the lower.

Other objects, features, and advantages will appear from the following description of preferred embodiments of the invention, taken together with the attached drawings thereof, in which:

FIG. 1 is a side elevational view, partially in section, of the presently preferred embodiment of the invention;

FIG. 2 is an end elevational view, partially in section, thereof;

FIG. 3 is a partial elevational view, partially in section, showing the side opposite to that shown in FIG. 1;

FIG. 4 is a sectional view at 4-4 of FIG. 2;

FIG. 5 is a partial side elevational view, partially in section, of a modified embodiment of the invention; and

FIG. 6 is a partial side elevational view, partially in section, of another modified embodiment of the invention.

Referring now more particularly to the drawings, there is shown in FIGS. 1 through 4 a grip indicated generally at 10. The grip 10 includes a frame 12, an actuator 14, and a core 16.

The frame 12 includes a downwardly extending pair of legs 18 and an upwardly extending externally threaded shank 20. '(While in the grip shown the legs and shank extend as indicated, it will be understood that frequently a pair of like grips are used respectively above and below a specimen being placed in tension, and that in such case the legs and shank of the frame of the lower grip would extend oppositely to that in the upper grip, shown in the figures. Elsewhere herein the words inner and outer ice are used to encompass not only both the abovementioned grip positions but others as well. Inner is used to mean in the direction of the mounting end, and outer to mean in the direction of the specimen-gripping end of the l Extending through a vertical hole through the crossportion 22 of frame 12 is core 16, which is limitedly axially and longitudinally slidable therein, but not rotatable therein, by virtue of pin 24 extending through a transverse hole in frame 12, the end of pin 24 resting in groove 26 of core 16. Above the shank 20, the core includes a flange 28 and, spaced therefrom thereabove, mounting portion 30 screw-threadedly secured to the rest of the core and including mounting hole 32.

The actuator 14 is downwardly generally cup-shaped, and includes a lower interiorly threaded portion 34, an upper end 36 including a hole through which core 16 extends, to permit free rotation of the actuator 14 relative to the core. The upper end 36 of the actuator is secured against undue axial movement between the flange 28 and the mounting portion 30 of the core. Handles 38 are provided to facilitate actuation.

The core 16 includes a lower portion 40 held in place by screws 42. The lower portion 40 includes a rearwardly offset vertical portion 44, from the lower extremity of which integrally extends forwardly from the portion 44 and transversely on each side thereof the guide member 46. A second guide member 48 is held yieldably limitedly away from the guide member 46 by pins 50, springs 52, and stops 54. The pins 50 are firmly mounted at their lower ends in guide member 46, and carry at their upper ends the stops 54; intermediately, they extend through the upper guide member 48, relative to which they are axially slidably movable. The springs press against the guide members 46 and 48, to ordinarily hold the latter away from the former and against stops 54. The guide member 46 includes a transverse guide surface 56 held at all times a fixed distance from the mounting hole 32. A second transverse guide surface 58 is provided on guide member 48.

Transversely slidable on guide members 46 and 48 are a pair of jaws 60. Each jaw 60 includes a transversely extending notch 62 rearwardly thereof, each notch including an upper transverse surface for slidable cooperation with the surface 58, a lower transverse surface for slidable cooperation with the surface 56, and a vertical transverse surface therebetween. The surfaces 56 and 58 are held apart by the springs 52 and stops 54 a distance to facilitate easy sliding contact simultaneously between the surfaces 56 and 58 and the mating surfaces of the notch 62. Each jaw 60 is pivotally connected by a pin 64 to one end of a link 66. At its other end, each link 66 is pivotally secured on a pin 68 in a slot 70 in a lower part of a leg 18 of the frame 12, the length of each link 66 being such that the faces 72 of the jaws 60 come together before the links are horizontal.

In operation, rotating the actuator clockwise (viewed from above in the embodiment made and positioned as shown) causes the frame 12 to rise. The guide member 46 holds the jaws 60 and pins 64 against rising, so that rising of the pins 68 carried by the frame brings the links 66 into a more nearly horizontal position, driving the jaws together. Rotating the actuator counterclockwise has the opposite effect. The faces or specimen-engaging portions 72 0f the jaws are at all times equidistant from the centerline of the grip, which coincides with the axis of the upper portion of the core, including the mounting portion 30 thereof, and of the hole through the cross-portion 22 of the frame. The jaw faces are also held at all times parallel to each other, completely free from flopping about, under firm control. Also, the jaws open and close with transverse or horizontal movement only; no longitudinal component puts undesired prec-ompression on a test specimen. Furthermore, the initial gripping force can be controlled within wide limits by the extent to which the actuator 14 is turned, and there is no tendency for this force to be relieved even in the event of specimen breakage, so that the jaws do not fly open and drop the specimen along with any instrument carried thereby.

In the preferred embodiment shown, the arrangement of the guide members, pins, springs, and stops permits additional holding force to be exerted during testing. The upper surfaces of the notches 62 act against guide member 48 after tension on a specimen held between the jaws has begun, and if tension is sufiicient it may move the guide member 48 downwardly toward the guide member 46. This permits the jaws 60 and therefore the pin 64 to move downwardly while ins 68 are stationary, tending to bring the links 66 still further toward the horizontal and to urge the jaws together with even greater force. Although breakage of a specimen of course returns the jaws to their initial gripping position, the original gripping force is still retained until purposely released by means of the actuator.

In FIG. is shown a modified embodiment featuring a toggle type actuator. In this embodiment the upwardly extending portion 120 of the frame (the remainder of which is as in the first embodiment, and is not shown) is externally cylindrical in shape, and carries a retaining washer =122. Secured by threads on core 116 is closure 124, which carries dependently therefrom therearound cuplike enclosure 126, through a hole in the bottom of which the frame portion 120 extends for axial movement relative thereto. A spring 128 extending between the retaining washer 122 and lower portions 120 of the enclosure 126 yieldingly upwardly biases the frame relative to the enclosure 126 (and thus the core 116). Core mounting portion 130 is threadedly secured to the lower part of core 116 above closure 124, and includes transverse mounting hole 132. Pivotal'ly mounted relative to core 116 in slot 134 thereof on pin 136 is toggle 138, which extends also through slots 140 and 142 in closure 124 and enclosure 126, respectively. Upward movement of the toggle 138 causes downward movement of its portion 144, which acts against the upper end 146 of the frame portion 120 to drive the frame downwardly relatively to the core (causing the jaws to open, in the manner already described in connection with downward frame movement for the first embodiment). Upon release of the toggle, the spring 128 drives the frame up, closing the jaws. This embodiment provides quick opening and quick return to the holding or gripping force characteristic of the pre-chosen spring 128.

A further embodiment is shown in FIG. 6, in which the actuator is of the air type. In this embodiment the upper portion of the frame (the lower portion of which is as shown in FIGS. 1 through 3) includes a lower cylindrical portion 220 and an upper threaded portion 222. Secured on the threaded portion is piston 224 carrying gasket 226. A closure 228 with vent hole 230 is secured on a threaded portion of the core 216, and core mounting portion 232 with mounting hole 234 is threadedly secured thereabove. Dependently secured to closure 228 is cuplike enclosure 236, the lower portion 238 of which carries gasket 240 airtightly sealing the same around frame portion 220. Air inlet 242 opens into the annular zone between frame portion 220 and enclosure 236. The frame portion 220 is downwardly biased by spring 244 extending from the upper surface of frame portion 220 .to the lower surface of closure 228. In this embodiment, air under any desired pressure is introduced through inlet 242 into annular zone 246. This drives the piston 224 upwardly, raising the frame and driving the jaws together with corresponding predetermined force. When the air pressure is released, the spring 244 and weight of the parts act to lower the frame and open the jaws. This embodiment has the advantage that gripping force on a specimen owing to the actuator alone remains constant even though extrusion of the specimen in the course of testing results in a diminution of specimen thickness.

Other embodiments of our combination invention within the scope of the appended claims will occur to those skilled in the art. We make no claim to have invented certain particular elements and features of the combination, namely provision of a core maintaining constant distance from a mounting portion to a transverse jaw guiding surface, and broadly causing jaws to open or close responsive to longitudinal movement of a frame relative to a core.

What we do claim is:

1. A testing machine grip comprising a longitudinally extending core including an inner mounting portion and longitudinally spaced transverse guide surfaces including an outwardly facing outer transverse guide surface at a fixed distance from said inner mounting portion and an inwardly facing inner transverse guide surface, a frame longitudinally movable relative to said core, an actuator for longitudinally moving said frame, a pair of jaws, and a pair of links, each said link being pivotally secured at one end in said frame and at its other end in one of said jaws, each said jaw including an outer transverse surface held in sliding relation against said outer transverse guide surface of said core and an inner transverse surface, said inner of said longitudinally spaced transverse surfaces of said core being supported by and held yieldably away from said outer transverse guide surface against said inner transverse surface of said jaw.

2. A testing machine grip comprising a longitudinally extending core including an inner mounting portion and an outwardly facing outer transverse surface at a fixed distance therefrom forming a transverse guide means, a frame longitudinally movable relative to said core, an actuator for longitudinally moving said frame, a pair of jaws, and a pair of links, each said link being pivotally secured at one end in said frame and at its other end in one of said jaws, each said jaw including a transverse surface held in sliding relation against said outer transverse surface of said transverse guide means of said core, said frame including an upwardly directed externally threaded portion, and said actuator including a mating internally threaded portion, said actuator being mounted on said core for free rotation there-on but not free longitudinal movement thereon.

3. A testing machine grip comprising a longitudinally extending core with an inner mounting portion and an outer guide portion, a frame longitudinally movable relative to said core, an actuator mounted on said core and cooperating with said frame to give the same longitudinal motion, a pair of jaws, and a pair of links, each of said links having one of its ends pivotally secured in said frame and its other end pivotally secured in one of said jaws, each of said jaws including a transverse notch characterized by 'longitudinally spaced inner and outer transverse notch surfaces, said guide portion of said core including a pair of transverse guide surfaces longitudinally spaced to guidingly permit sliding movement thereon of said transverse notch surfaces, the innner of said pair of transverse guide surfaces of said core being limitedly yieldably held away from the outer of the last-mentioned pair, the outer thereof being fixedly longitudinally spaced from said mounting portion.

4. A testing machine grip comprising a longitudinally extending core with an inner mounting portion and an outer guide portion, a frame longitudinally movable relative to said core, an actuator mounted on said core and cooperating with said frame to give the same longitudinal motion, a pair of jaws, and a pair of links, each of said 'links having one of its ends pivotally secured in said frame and its other end pivotally secured in one of said jaws, each of said jaws including a transverse notch characterized by longitudinally spaced inner and outer transverse notch surfaces, said guide portion of said core including a pair of transverse guide surfaces longitudinally spaced to guidingly permit sliding movement thereon of said transverse notch surfaces, the outer of said pair of transverse guide surfaces being on an outer guide member and the inner thereof on an inner guide member, said outer guide member being fixedly longitudinally spaced from said mounting portion, said grip including means carried by said outer guide member on which said inner guide member is longitudinally slidably mounted, stop means for limiting the extent of longitudinal movement of said inner guide member away from said 'outer guide member, and means for yieldingly urging said guide members longitudinally apart.

5. A testing machine grip comprising a longitudinally extending core including an inner mounting portion and an outwardly facing outer transverse surface at a fixed distance therefrom forming a transverse guide means, a frame longitudinally movable relative to said core, an actuator for longitudinally moving said frame, a pair of jaws, and a pair of links, each said link being pivotally secured at one end in said frame and at its other end in one of said jaws, each said jaw including a transverse surface held in sliding relation against said outer transverse surface of said transverse guide means of said core, and said core and said frame being connected by said actuator, said actuator cooperating with each thereof to produce longitudinal relative movement therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,157,345 5/39 Nelson 269236 X 2,495,954 1/50 Bailey 29428 X 3,015,131 1/62 Hehl 74-110 X RICHARD C. QUEISSER, Primary Examiner.

JOSEPH P. STRIZAK, Examiner. 

1. A TESTING MACHING GRIP COMPRISING A LONGITUDINALLY EXTENDING CORE INCLUDING AN INNER MOUNTING PORTION AND LONGITUDINALLY SPACED TRANSVERSE GUIDE SURFACES INCLUDING AN OUTWARDLY FACING OUTER TRANSVERSE GUIDE SURFACE AT A FIXED DISTANCE FROM SAID INNER MOUNTING PORTION AND AN INWARDLY FACING INNER TRANSVERSE GUIDE SURFACE, A FRAME LONGITUDINALLY MOVABLE RELATIVE TO SAID CORE, AN ACTUATOR FOR LONGITUDINALLY MOVING SAID FRAME, A PAIR OF JAWS, AND A PAIR OF LINKS, EACH SAID LINK BEING PIVOTALLY SECURED AT ONE END IN SAID FRAME AND AT ITS OTHER END IN ONE OF SAID JAWS, EACH SAID JAW INCLUDING AN OUTER TRANSVERSE SURFACE HELD IN SLIDING RELATION AGAINST SAID OUTER TRANSVERSE GUIDE SURFACE OF SAID CORE AND AN INNER TRANSVERSE SURFACE, SAID INNER OF SAID LONGITUDINALLY SPACED TRANSVERSE SURFACES OF SAID CORE BEING SUPPORTED BY AND HELD YIELDABLY AWAY FROM SAID OUTER TRANSVERSE GUIDE SURFACE AGAINST SAID INNER TRANSVERSE SURFACE OF SAID JAW. 